In this particular case RTFM is not a very helpful answer given the multiple levels of finds settings; it is particularly confusing trying to figure out if the -o is associated with -type or -perm.
– LighthartNov 9 '15 at 23:27

I allow myself to disagree. The question was "What does the -o do? Does it mean something like OR?". This is perfectly answered by the man page: " expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true."
– 0x89Nov 10 '15 at 8:17

Btw. your question about precedence is handled in the same paragraph of the man page: "OPERATORS Listed in order of decreasing precedence" and "Two expressions in a row are taken to be joined with an implied 'and'; expr2 is not evaluated if expr1 is false.").
– 0x89Nov 10 '15 at 8:24

Everything depends on what do you consider 'incorrect permission'. man find helps you by defining the way how you can look for files/dirs with given permission:

-perm -mode
All of the permission bits mode are set for the file. Symbolic modes are
accepted in this form, and this is usually the way in which would want to
use them. You must specify ‘u’, ‘g’ or ‘o’ if you use a symbolic mode.
See the EXAMPLES section for some illustrative examples.
-perm /mode
Any of the permission bits mode are set for the file. Symbolic modes are
accepted in this form. You must specify ‘u’, ‘g’ or ‘o’ if you use a
symbolic mode. See the EXAMPLES section for some illustrative examples.
If no permission bits in mode are set, this test matches any file (the
idea here is to be consistent with the behaviour of -perm -000).
-perm +mode
Deprecated, old way of searching for files with any of the permission
bits in mode set. You should use -perm /mode instead. Trying to use the
‘+’ syntax with symbolic modes will yield surprising results. For exam‐
ple, ‘+u+x’ is a valid symbolic mode (equivalent to +u,+x, i.e. 0111) and
will therefore not be evaluated as -perm +mode but instead as the exact
mode specifier -perm mode and so it matches files with exact permissions
0111 instead of files with any execute bit set. If you found this para‐
graph confusing, you’re not alone - just use -perm /mode. This form of
the -perm test is deprecated because the POSIX specification requires the
interpretation of a leading ‘+’ as being part of a symbolic mode, and so
we switched to using ‘/’ instead.